Magnesium hydroxide is used in large quantities in various applications including toothpaste additives and as an acid neutralizer. Magnesium hydroxide Mg(OH).sub.2 ! is also the precursor in the manufacture of magnesium oxide (MgO) which is used in antacid formulations and as a pigment in the paper industry. It is desirable to be able to ship and store magnesium hydroxide as a high solids aqueous slurry. However, these slurries are fairly unstable and form either gels or hard-pack sediment upon standing, thereby rendering the slurries difficult to use and potentially damaging to piping, pumps, and other slurry handling mechanical equipment.
Magnesium hydroxide and magnesium oxide slurry stability has been the subject of extensive research and has been a long standing problem for the magnesium hydroxide industry. The art has addressed the problem by focusing on methods of reducing the viscosity of high solids magnesium hydroxide slurries. U.S. Pat. No. 4,230,610 teaches a method of reducing the viscosity of magnesium oxide slurries by using 0.1 to 5.0 percent by weight of poly(acrylic acid) neutralized to a pH of from about 8.0 to about 12.0. U.S. Pat. No. 4,375,526 teaches a method of reducing the viscosity and enhancing the stability of magnesium hydroxide slurries by using anionic polymers and copolymers. U.S. Pat. No. 4,430,248 teaches a method of reducing the viscosity of magnesium hydroxide slurries by using cationic polymers and copolymers.
Those approaches are somewhat effective in reducing the viscosity of magnesium oxide and magnesium hydroxide slurries but I have found that these approaches are not satisfactory for maintaining the stability of the slurries over an extended period of time.
It is an object of this invention to provide a method of preparing stable aqueous slurries of magnesium hydroxide.